Sinclair ZX80 / ZX81 / Z88 Forums

Sometimes I also get a black square then this So, I really am guessing memory.
Typing at this point seems to do nothing.

Okay. It turns out the keyboard membrane may just be bad.

I removed the keyboard and used a jumper wire to "type" by connect between the two headers. Once I did this I got the inverted K and was even able to write a little program (PRINT 1 <ENTER>)

So, I know the headers are good, the Z80 is good, the ULA is good, and the ROM is good.

One thing that worries me is that the leads in the keyboard membrane look scorched.
The tips that connect to the headers are black, and part of the wires look annealed

I have seen that effect in keyboard membranes a few times in otherwise fine computers.

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